In the field of graphic arts, an image formation system capable of giving a photographic characteristic of high contrast is required, enough to attain a good regeneration of a dot image of continuous gradation as well as a good regeneration of a line image.
A specific developer called a lith-developer has heretofore been used for the purpose. The lith-developer contains only hydroquinone as a developing agent, and uses a sulfite preservative in the form of an adduct of a sulfite with formaldehyde in order to keep extremely low concentration of the free sulfite ion in the developer, whereby the infectious developability is not deteriorated. Thus, the lith-developer is extremely easily oxidized with air and difficult to withstand a preservation of over three days, which is a serious defect.
Methods for obtaining a photographic characteristic of high contrast by the use of a stable developer are disclosed in U.S. Pat. Nos. 4,224,401, 4,168,977, 4,166,742, 4,311,781, 4,272,606, 4,211,857, and 4,243,739, where a hydrazine derivative is used. According to the methods, a photographic characteristic of high contrast and high sensitivity may be obtained, and moreover, addition of a sulfite of high concentration to a developer is possible. Accordingly, the stability of the developer against air-oxidation is markedly improved, as compared with the lith-developer.
In the methods using a hydrazine derivative, however, the pH value of the developer is kept higher than that of a conventional lith-developer, and therefore, the pH value of the developer is variable, resulting in a variation of the developed photographic characteristics. This is a troublesome problem.
U.S. Pat. No. 4,269,929 discloses, in order to solve said problem to use an alkaline developer containing a dihydroxy-benzene developing agent and a 3-pyrazolidone developing agent, to which an amine compound is added so as to improve the activity of the developer; whereby the hydrazine derivative exerts effects of sensitization and producing high contrast image by the developer having a lower pH value.
It is impossible, however, to sufficiently lower the pH value of the developer enough to stop the variation of the pH value under the condition of a general preservation or use, even by the method.
In addition, the amino compounds added to the developer act as a solvent of a silver halide (refer to The Theory of the Photographic Process, 3rd Ed., p. 370, written by C. E. K. Mees, and Photographic Processing Chemistry, p.43, written by L. F. A. Mason). Under the circumstances, the method for the development using a large amount of amino compounds as disclosed in the U. S. patent has a problem of a so-called "silver stain". The "silver stain" is a defective phenomenon which occurs during development by a transfer of silver, which is depositioned or precipitated on the surface of a wall of the development tank or of a roller of a film conveyor from a silver halide dissolved in a developer, to a fresh film to be newly developed, wherein the developer is used in a development method using an automatic developing apparatus where a supplementary developer solution is fed into a development tank, in accordance with the area of the film to be developed and, the developer in the tank is used for a long period of time.
U.S. Pat. No. 4,740,452 also discloses an alkaline developer composition containing a developing agent, a preservative and an amino compound taught to avoid the staining problems of the prior art processes and products. However, this prior art composition must be employed at a relatively high pH which causes stability problems in the employment of the developer composition.
In order to overcome both the silver stain and instability problems encountered in the use of the prior art developer compositions, we have discovered the instant developer composition to be eminently successful.